Operation amount acquisition device

This application claims priority from Japanese Patent Application No. 2023-198714 filed on Nov. 23, 2023. The entire content of the priority application is incorporated herein by reference.

The following disclosure relates to an operation amount acquisition device that acquires an operation amount of an actuator.

In a steering system described in Japanese Patent Application No. 2017-197073 (JP 2017-197073 A), when a difference between an actual yaw rate and a front wheel yaw rate is smaller than a set value or when a difference between the actual yaw rate and a rear wheel yaw rate is smaller than the set value, it is determined that the steering system is in a neutral state. Further, a deviation in the neutral state of the steering system between an estimated steering angle estimated based on a yaw rate and a detected steering angle detected by a steering angle sensor is stored. The set value is a value obtained by subtracting an error of a yaw rate sensor from a threshold value. The steering angle is an operation angle of a steering wheel.

An aspect of the present disclosure relates to an operation amount acquisition device capable of favorably acquiring an operation amount of an actuator.

In the operation amount acquisition device according to the present disclosure, the operation amount is acquired based on a first physical quantity detected by a first physical quantity detecting device when a vehicle is traveling in a predetermined set state while the actuator is controlled based on the operation amount detected by an operation amount detecting device.

A change in the first physical quantity is large relative to a change in the operation amount. Thus, validity of the operation amount detected by the operation amount detecting device can be favorably acquired based on the first physical quantity when the vehicle is traveling in the set state. Accordingly, the operation amount can be favorably acquired by acquiring the operation amount based on the first physical quantity when the vehicle is traveling in the set state.

Hereinafter, an operation amount acquisition device according to an embodiment of the present disclosure will be described with reference to the drawings. The operation amount acquisition device acquires an operation amount of an actuator included in a rear wheel steering system provided in a vehicle.

1 2 FIGS.and 4 6 4 10 10 6 12 12 As shown in, the vehicle includes a rear wheel steering (Dynamic Rear Steering) system, an electric power steering (EPS) system, and the like. The rear wheel steering systemsteers a left rear wheelL and a right rear wheelR. The electric power steering systemsteers a left front wheelL and a right front wheelR.

10 10 10 10 12 12 12 12 6 6 Hereinafter, the left rear wheelL and the right rear wheelR are abbreviated as left and right rear wheelsL,R, and the left front wheelL and the right front wheelR are abbreviated as left and right front wheelsL,R. The electric power steering systemis abbreviated as an EPS system.

4 20 22 24 20 22 26 26 22 10 10 26 26 The rear wheel steering systemincludes a housing, a steering rod, a moving force applying device, and the like. The housingextends in a width direction of the vehicle and is held by a vehicle body side member (not shown). The steering rodextends in a direction parallel to an axis L. Tie rodsL,R are respectively connected to opposite ends of the steering rod. The left and right rear wheelsL,R are respectively connected to the tie rodsL,R. The axis L extends in the width direction of the vehicle. Hereinafter, the direction parallel to the axis L is referred to as an axial direction.

22 20 22 20 22 22 s The steering rodis held by the housingso as to be relatively movable in the axial direction and relatively unrotatable about the axis L. The steering rodis held by the housingthrough spline engagement, for instance. A male screw portionis provided at an intermediate portion of the steering rod.

24 22 24 30 32 34 30 36 36 36 36 32 36 a b b. The moving force applying deviceapplies a moving force, which is a force in the axial direction, to the steering rod. The moving force applying deviceincludes an actuator, a nut member, a motion converting mechanism, and the like. The actuatorincludes an electric motorand the like. The electric motorincludes a statorand a rotary shaft portion. The nut memberis provided so as to be rotatable integrally with the rotary shaft portion

36 20 38 39 36 20 44 32 20 36 32 20 20 36 36 36 22 36 22 22 32 32 a b b b a b b s s The statoris fixed to the housing. A pair of bearingsandare provided between the rotary shaft portionand the housing. A bearingis provided between the nut memberand the housing. As a result, the rotary shaft portionand the nut memberare held by the housingso as to be relatively immovable in the axial direction and relatively rotatable about the axis L relative to the housing. The rotary shaft portionis provided radially inward of the statorso as to extend in the axial direction. The rotary shaft portionhas a hollow shape, and the steering rodpenetrates through a central portion of the rotary shaft portion. The male screw portionof the steering rodis screwed to a female screw portionprovided on an inner circumferential surface of the nut member.

30 36 The actuatormay include a speed reducer that reduces a rotational speed of the electric motor.

34 32 32 22 22 s s In the present embodiment, the motion converting mechanismis constituted by the female screw portionof the nut member, the male screw portionof the steering rod, and the like.

32 30 22 10 10 26 26 22 30 10 10 30 30 22 22 10 10 12 12 In the steering system, when the nut memberis rotated by the actuator, the steering rodis moved in the axial direction, and the left and right rear wheelsL,R are steered via the tie rodsL,R, respectively. In the present embodiment, when the steering rodis located at a neutral position thereof, for example, the actuatoris located at a neutral position thereof. A steering angle of the left and right rear wheelsL,R in this case is 0°. Further, a cumulative number of rotations of the actuator(which will be referred to as a cumulative rotation number of the actuatorwhere appropriate) when the steering rodis located at the neutral position is 0, and a displacement of the steering rodfrom the neutral position is 0. Hereinafter, the steering angle of the left and right rear wheelsL,R will be referred to as a rear wheel steering angle where appropriate. Similarly, a steering angle of the left and right front wheelsL,R will be referred to as a front wheel steering angle where appropriate.

30 22 4 22 10 10 30 32 In the present embodiment, the cumulative rotation number of the actuatorfrom the neutral position, the displacement (movement amount) of the steering rodfrom the neutral position, and the rear wheel steering angle correspond to each other on a one-to-one basis. In the rear wheel steering systemaccording to the present embodiment, it is assumed that the steering rodis moved by 0.1 mm and the left and right rear wheelsL,R are steered by 0.1° by one rotation of the actuator(the nut member), for example.

4 50 50 50 50 50 52 54 56 58 50 c m f f. The rear wheel steering systemis provided with a rear wheel steering Electronic Control Unit (ECU)mainly composed of a computer. The rear wheel steering ECUincludes an execution portion, a storage portion, an input/output portion, for example. A resolver, an absolute angle sensor, a database, a lateral acceleration sensor, and the like are connected to the input/output portion

52 30 52 52 30 52 30 The resolveris one example of a rotation-number detecting device that detects the number of rotations of the actuator. In the present embodiment, the number of rotations detected by the resolveris accumulated to obtain a cumulative rotation number Nc. The resolveris capable of accurately detecting the number of rotations of the actuator. A tolerance of the resolveris smaller than one rotation of the actuator. The tolerance refers to an allowable variation of a value detected by a sensor.

54 22 20 54 22 22 22 22 The absolute angle sensordetects a position of the steering rodrelative to the housing. In the present embodiment, the absolute angle sensordetects the displacement of the steering rodfrom the neutral position. Though the neutral position of the steering rodis acquired in advance before shipment of the vehicle, it is also acquired and learned after traveling. The displacement of the steering rodfrom the neutral position will be referred to as a position of the steering rodor a rod position.

3 FIG. 54 22 54 54 22 30 As shown in, the absolute angle sensorhas low detection accuracy of the displacement of the steering rodfrom the neutral position. A tolerance of the absolute angle sensoris ±0.15 mm. It is thus difficult for the absolute angle sensorto detect a change in the position of the steering rodcorresponding to one rotation of the actuator.

56 50 50 56 100 100 70 The databasemay be connected to the rear wheel steering ECU(i.e., externally attached) or may be built in the rear wheel steering ECU. The databasestores an OFF-time cumulative rotation number Ne, an OFF-time rod position Pe, a straight-traveling operation amount d, and the like. The OFF-time cumulative rotation number Ne is a cumulative rotation number when a main switchis switched from ON to OFF. The OFF-time rod position Pe is the rod position when the main switchis switched from ON to OFF. The OFF-time rod position Pe is acquired based on the OFF-time cumulative rotation number Ne. The straight-traveling operation amount d is an operation amount of a steering operation memberfrom its neutral position when the vehicle is traveling straight.

58 The lateral acceleration sensordetects lateral acceleration that acts on the vehicle. When the vehicle travels straight on a flat road surface, the lateral acceleration is smaller than a set value. When the vehicle travels on an inclined road surface (cant), however, the lateral acceleration is larger than the set value even if the vehicle travels straight. Further, the lateral acceleration is larger than the set value also when the vehicle body is in a roll posture.

6 70 12 12 6 70 70 72 70 70 70 The EPS systemassists an operation force applied to the steering operation memberto steer the left and right front wheelsL,R. The EPS systemapplies an assist force corresponding to an operation amount θ of the steering operation memberfrom its neutral position. The operation amount θ of the steering operation memberfrom the neutral position is detected by an operation state detecting device. The steering operation memberis operable by a driver of the vehicle. The steering operation membermay be a steering wheel, for example, but is not limited to the steering wheel. In a case where the steering operation memberis the steering wheel, the operation amount may be referred to as an operation angle.

6 60 62 64 70 76 78 64 70 64 78 60 60 The EPS systemmay include, for example, an electric power steering ECU, a housing, a steering rod, and a moving force applying device (not shown). The steering operation memberis connected to a steering shaftand a gear box. The steering rodis provided with a rack portion (not shown). The steering operation memberis engaged with the rack portion of the steering rodin the gear box. Hereinafter, the electric power steering ECUwill be abbreviated as an EPS ECU.

60 72 82 84 86 60 86 86 The EPS ECUincludes a computer as a main component. The operation state detecting device, a resolver, an absolute angle sensor, a yaw rate sensor, and the like are connected to an input/output portion of the EPS ECU. The yaw rate sensordetects a yaw rate. The yaw rate is a rotational speed around a vertical axis of the vehicle. When the yaw rate detected by the yaw rate sensoris equal to or less than a set value, it can be estimated that the vehicle is in a straight traveling state.

70 64 70 In the present embodiment, when the steering operation memberis located at the neutral position, it is considered that the steering rodis located at the neutral position and the front wheel steering angle is 0. Further, when the operation amount of the steering operation memberis 1.5°, the front wheel steering angle is considered to be approximately 0.1°.

86 70 72 In the present embodiment, when a state in which a detection value γ of the yaw rate sensoris smaller than a set value γth continues for a set time or more, for example, it is determined that the vehicle is in the straight traveling state. The straight traveling state is one example of a set state. When the vehicle is in the straight traveling state, the operation amount θ of the steering operation memberis detected by the operation state detecting deviceto acquire the straight-traveling operation amount d. The straight-traveling operation amount d is appropriately updated and learned.

60 9 FIG. In the EPS ECU, a straight-traveling operation amount acquisition program represented by a flowchart ofis executed every set time when the vehicle is in a traveling state.

201 201 201 70 72 202 203 In Step, it is determined whether or not the vehicle is in the straight traveling state. (Hereinafter, Stepwill be abbreviated as S. The same applies to the other steps). If the determination is YES, the operation amount θ of the steering operation memberis detected by the operation state detecting devicein S, and the straight-traveling operation amount d is acquired and stored by learning in S.

50 60 90 91 92 94 90 92 92 50 60 91 92 94 A plurality of ECUs such as the rear wheel steering ECUand the EPS ECUare connected to each other via a controller area network (CAN). A drive ECU, an automated driving assistance ECU, a travel control ECU, and the like are connected to the CAN. The automated driving assistance ECUwill be also referred to as an advanced driver-assistance system (ADAS) ECU. The rear wheel steering ECU, the EPS ECU, the drive ECU, the automated driving assistance ECU, the travel control ECU, and the like are communicable with each other.

91 100 91 100 50 90 100 The drive ECUcontrols a drive device (not shown) of the vehicle. The main switchand the like of the vehicle are connected to the drive ECU. Information indicating an ON or OFF state of the main switchis supplied to the rear wheel steering ECUand the like via the CAN. The main switchmay be, for example, an ignition switch.

92 102 92 102 102 50 90 The automated driving assistance ECUassists traveling of the vehicle. The assistance of traveling of the vehicle includes assistance of driving of the vehicle. A surrounding environment acquisition deviceand the like are connected to the automated driving assistance ECU. The surrounding environment acquisition deviceacquires, for example, a surrounding object that is an object located around an own vehicle that is the vehicle, so as to acquire a relative positional relationship between the own vehicle and the surrounding object. The surrounding environment acquisition deviceincludes, for example, a camera. Information indicating the relative positional relationship between the own vehicle and the surrounding object is supplied to the rear wheel steering ECUand the like via the CAN.

94 94 104 94 104 12 12 10 10 104 12 12 10 10 104 50 90 The travel control ECUstabilizes traveling of the vehicle. Thus, the travel control ECUmay be referred to as a vehicle stability control ECU. Wheel speed sensorsare connected to the travel control ECU. The wheel speed sensorsare provided respectively for the left and right front wheelsL,R and the left and right rear wheelsL,R. Each wheel speed sensordetects a rotational speed of a corresponding one of the left and right front wheelsL,R and the left and right rear wheelsL,R. Based on the detection values of the wheel speed sensors, a traveling speed v of the vehicle is detected. Information indicating the traveling speed v of the vehicle is supplied to the rear wheel steering ECUand the like via the CAN.

50 10 10 70 An operation of the vehicle configured as described above will be described. The rear wheel steering ECUdetermines a target rear wheel steering angle that is a target steering angle of the left and right rear wheelsL,R. The target rear wheel steering angle may be determined based on the relative positional relationship between the surrounding object and the own vehicle or may be determined based on the operation amount θ of the steering operation memberand the traveling speed v of the vehicle, and the like. The target rear wheel steering angle may be determined to be in the same phase with respect to a target front wheel steering angle or may be determined to be in a reverse phase with respect to the target front wheel steering angle.

50 100 30 52 30 22 30 30 In the rear wheel steering ECU, while the main switchis ON, the number of rotations of the actuatoris detected by the resolverand the cumulative rotation number of the actuatoris acquired. The position of the steering rodis acquired based on the cumulative rotation number of the actuator, and the rear wheel steering angle is acquired. Then, the actuatoris controlled such that the acquired rear wheel steering angle approaches the target rear wheel steering angle.

100 30 52 100 56 56 100 30 Ne→Ncf On the other hand, while the main switchis OFF, the number of rotations of the actuatoris not detected by the resolver. Thus, the OFF-time cumulative rotation number Ne, which is the cumulative rotation number when the main switchis switched from ON to OFF, is stored in the database, for example. As described above, the OFF-time rod position Pe is also stored in the database. Next, when the main switchis switched from OFF to ON, counting of the cumulative rotation number of the actuatoris considered to be started by setting the OFF-time cumulative rotation number Ne as a count start value Ncf.

100 30 22 4 22 22 However, when an external force is applied to the vehicle body while the main switchis OFF and the actuatoris in a stopped state, for example, the steering rodmay be moved in the rear wheel steering system. This may be expressed as the steering rodbeing “moved” or a “movement” of the steering rodbeing caused.

70 22 4 64 6 For example, there are considered a case in which a large force is applied to a rear portion of the vehicle body and a case in which vibration occurs due to the vehicle being carried by a carrier car and the operation of the steering operation memberis locked. In these cases, the steering rodmay be moved in the rear wheel steering systemwhile the steering rodis hardly moved in the EPS system.

30 100 30 When the “movement” is caused as described above, an actual cumulative rotation number of the actuatorat the time when the main switchis turned to ON is different from the OFF-time cumulative rotation number Ne. Therefore, if the OFF-time cumulative rotation number Ne is set as the count start value Ncf, the cumulative rotation number of the actuatoris different from the actual cumulative rotation number. The rear wheel steering angle cannot be accurately acquired, and it is difficult to accurately control the rear wheel steering angle.

100 22 54 100 22 Therefore, when the main switchis switched from OFF to ON, the position of the steered rodis detected by the absolute angle sensor, and the detected rod position is defined as an ON-time rod position Ps. It is then determined whether or not an absolute value |Pe−Ps| of a difference between the OFF-time rod position Pe and the ON-time rod position Ps is larger than a determination threshold value ΔPth. When the absolute value |Pe−Ps| of the difference is larger than the determination threshold value ΔPth, it is determined that the “movement” has been caused in a time period during which the main switchis OFF. The determination threshold ΔPth may be a value by which the steering rodcan be considered to have been moved by an external force. The determination threshold ΔPth is one example of a second threshold.

100 22 100 Ns→Ncf In the case where the “movement” has been caused in the time period during which the main switchis OFF, the steering rodis considered to be located at the ON-time rod position Ps when the main switchis switched from OFF to ON. Therefore, based on the ON-time rod position Ps, a cumulative rotation number Ns is acquired and is set as an ON-time cumulative rotation number Ns. Then, the ON-time cumulative rotation number Ns is set as the count start value Ncf.

30 30 54 Then, the cumulative rotation number of the actuatoris counted from the count start value Ncf. This can be considered that the cumulative rotation number Ne of the actuatoris corrected based on the detection value of the absolute angle sensor.

50 5 FIG. In the rear wheel steering ECU, a rear wheel steering angle control program represented by a flowchart ofis executed every set time.

101 100 102 108 In S, it is determined whether or not the main switchis switched from OFF to ON. When the determination is YES, S-Sare executed.

102 56 103 54 104 105 106 In S, the OFF-time cumulative rotation number Ne and the OFF-time rod position Pe are read from the database. In S, the ON-time rod position Ps is detected by the absolute angle sensor. In S, it is determined whether or not the absolute value |Pe−Ps| of the difference is larger than the determination threshold value ΔPth. When the determination is NO, the OFF-time cumulative rotation number Ne is set as the count start value Ncf in S, and the counting of the cumulative rotation number Nc is started from the count start value Ncf in S.

104 107 108 30 When the determination in Sis YES, on the other hand, the control flow proceeds to Sin which the ON-time cumulative rotation number Ns is determined based on the ON-time rod position Ps and the ON-time cumulative rotation number Ns is set as the count start value Ncf. In S, the counting of the cumulative rotation number of the actuatoris started from the count start value Ncf.

101 109 100 101 109 110 102 108 When the determination in Sis NO, it is determined in Swhether or not the main switchis in the ON state. When the determination in Sis NO and the determination in Sis YES, Sand subsequent steps are executed without executing S-S.

110 111 22 30 Next, it is determined in Swhether or not the vehicle is started to travel. When the determination is YES, the rear wheel steering angle is controlled in S. The position of the steering rodis acquired based on the cumulative rotation number Nc, and the rear wheel steering angle is acquired. Then, the actuatoris controlled such that the rear wheel steering angle approaches the target rear wheel steering angle.

112 113 100 112 111 113 110 113 112 113 114 116 In S, it is determined whether or not the traveling of the vehicle is ended. In S, it is determined whether or not the main switchis turned to OFF. When the determination in Sis NO, Sis repeatedly executed. When the determination in Sis NO, S-Sare repeatedly executed. When the determinations in Sand Sare YES, S-Sare executed.

114 115 116 56 In S, the counting of the cumulative rotation number Nc is ended. In S, the OFF-time cumulative rotation number Ne is acquired, and the OFF-time rod position Pe is acquired. In S, these are stored in the database.

54 22 54 Since the tolerance of the absolute angle sensoris large as described above, however, it is difficult to accurately detect a displacement of the steering rodby an amount of 0.15 mm or less. Even if the cumulative rotation number is corrected based on the detection value of the absolute angle sensor, the corrected cumulative rotation number may be different from the actual cumulative rotation number. It is difficult to accurately control the rear wheel steering angle.

70 12 12 Even if the rear wheel steering angle is controlled to be 0° and the front wheel steering angle is controlled to be 0°, for example, the rear wheel steering angle may not be 0° even though the front wheel steering angle is controlled to be 0°. In this case, when straight traveling is desired, the steering operation memberis operated, and the left and right front wheelsL,R are also steered.

4 FIG. 4 FIG. 10 10 12 12 In a case where the front wheel steering angle and the rear wheel steering angle are equal to each other, the vehicle performs deflected traveling, as shown in. The deflected traveling refers to straight traveling in a state in which an axis Lf extending in the front-rear direction of the vehicle body is inclined with respect to a traveling direction F of the vehicle, as shown in. Since the vehicle travels straight in the direction of the wheelsL,R,L,R, the traveling direction of the vehicle is F. In the deflected traveling, on the other hand, the axis Lf extending in the front-rear direction of the vehicle body is inclined with respect to the traveling direction F. The axis Lf extending in the front-rear direction of the vehicle body is referred to as a front-rear direction axis.

70 It is apparent from the above that the straight-traveling operation amount d, which is the operation amount of the steering operation member, is larger when the rear wheel steering angle is large than when the rear wheel steering angle is small. Further, the front wheel steering angle can be acquired based on the straight-traveling operation amount d, and the rear wheel steering angle can be similarly acquired.

70 30 30 In the present embodiment, the rear wheel steering angle is acquired based on the operation amount (the straight-traveling operation amount d) of the steering operation memberin a state in which the rear wheel steering angle is controlled such that the vehicle travels straight. Based on the rear wheel steering angle, the actual cumulative rotation number of the actuatoris acquired, and the cumulative rotation number is corrected. In the present embodiment, the cumulative rotation number Nc of the actuatoris corrected based on the straight-traveling operation amount d.

70 70 70 70 10 10 72 70 72 In a case where the steering operation memberis a steering wheel, the steering wheelcan be rotated from a neutral position thereof by about 360° to 540° in one direction. Even in a case where the steering operation memberis not the steering wheel, a maximum operation amount of the steering operation memberto one side is usually larger than a maximum steering angle of the left and right rear wheelsL,R to one direction. The operation state detecting devicecan accurately detect 1.5°, which is the operation amount of the steering operation member. The operation state detecting devicehas a tolerance smaller than ±1.5°.

12 12 10 10 30 4 From the above, in a case where the straight-traveling operation amount d is ±1.5°, for example, it can be estimated that the left and right front wheelsL,R and the left and right rear wheelsL,R are steered by ±0.1°. This causes a difference corresponding to ±1 rotation of the cumulative rotation number Nc of the actuatorin the rear wheel steering system. Thus, in the case where the straight-traveling operation amount d is ±1.5°, the cumulative rotation number Nc is corrected by ±1.

4 6 The numerical values such as 0.1°, 1.5°, and 0.1 mm are described by way of example in the present description, and the values are not limited to those described above. By changing specifications of the rear wheel steering systemand the EPS system, these numerical values also change.

100 56 100 22 In the present embodiment, an absolute value |d−dm| of a difference between the straight-traveling operation amount d detected when the main switchis ON this time and the straight-traveling operation amount dm stored in the databasewhen the main switchis ON last time is acquired. Then, it is determined whether or not the absolute value |d−dm| of the difference between the straight-traveling operation amounts is larger than a first threshold value dth, and it is determined whether or not a movement amount conversion value ΔPd is smaller than a third threshold value δ. The movement amount conversion value ΔPd is a value acquired by converting the absolute value |d−dm| of the difference into the movement amount of the steering rod.

d−dm|>dth Pd<δ When the absolute value |d−dm| of the difference is larger than the first threshold dth and the movement amount conversion value ΔPd is smaller than the third threshold δ, the cumulative rotation number Nc is corrected based on the straight-traveling operation amount dm.|Δ

56 54 100 54 54 The first threshold value dth is set to a value by which the vehicle can be considered to be in a state of deflected traveling, i.e., a deflected traveling state. The straight-traveling operation amount dm stored in the databaseis considered to be substantially 0°. On the other hand, an absolute value of the straight-traveling operation amount d is large when the vehicle is in the deflected traveling state this time. The third threshold value δ is set to a value determined based on the tolerance of the absolute angle sensor. When the main switchis switched from OFF to ON, a difference equal to or larger than the tolerance of the absolute angle sensorhas already been corrected. Therefore, the reason why the difference equal to or larger than the tolerance of the absolute angle sensoris generated again is that the reliability of the value of the straight-traveling operation amount d is considered to be low.

6 FIG. 12 12 10 10 At the time of shipment of the vehicle, at the time of inspection of the vehicle, etc., an alignment adjustment program represented by a flowchart ofis executed. The alignment adjustment is performed for both the left and right front wheelsL,R and the left and right rear wheelsL,R.

1 4 2 56 3 30 4 In S, an alignment adjustment mode is set in the rear wheel steering system. In S, data such as the straight-traveling operation amount d stored in the databaseis deleted. In S, the counting of the cumulative rotation number of the actuatoris started. In S, the alignment adjustment is performed.

5 58 6 7 70 6 7 6 7 8 56 9 It is then determined in Swhether or not the vehicle is started to travel. Based on the lateral acceleration detected by the lateral acceleration sensor, it is determined in Swhether or not a road surface is a special road surface such as a cant, and it is determined in Swhether or not there is a circumstance in which the vehicle is in a roll posture, for instance. This is because there is a high possibility that the operation amount θ of the steering operation memberin the straight traveling state of the vehicle does not accurately reflect the rear wheel steering angle when the lateral acceleration is greater than a set value even if the vehicle is in the straight traveling state. When the road surface on which the vehicle travels is not the special road surface and the inclination of the vehicle in the lateral direction is small, the determinations in Sand Sare NO. When the determinations in Sand Sare NO, the straight-traveling operation amount d is received in Sand stored in the databasein S.

60 56 In the present embodiment, when the vehicle is in the straight traveling state and the vehicle is not inclined, information indicating the straight-traveling operation amount d supplied from the EPS ECUis received, and the information is stored and updated in the database.

10 11 100 10 11 10 11 5 11 10 11 It is determined in Swhether or not the traveling of the vehicle is ended. It is determined in Swhether or not the main switchis turned to OFF. When the straight-traveling operation amount d is acquired once from the start of traveling to the end of traveling, Sand Sare repeatedly executed until the determinations in Sand Sbecome YES. On the other hand, when the straight-traveling operation amount d is acquired a plurality of times, S-Smay be repeatedly executed while the determinations in Sand Sare NO.

10 11 12 13 14 56 15 When the determinations in Sand Sare YES, the counting of the rotation number is ended in S. In S, the OFF-time cumulative rotation number Ne and the OFF-time rod position Pe are acquired. In S, the OFF-time cumulative rotation number Ne and the OFF-time rod position Pe are stored in the database. Thereafter, the alignment adjustment mode is canceled in S.

50 21 100 22 23 54 24 24 51 24 25 30 7 8 FIGS.and In the rear wheel steering ECU, an operation amount acquisition program represented by flowcharts ofis executed every set time. In S, it is determined whether or not the main switchis switched from OFF to ON. When the determination is YES, the OFF-time cumulative rotation number Ne and the OFF-time rod position Pe are read in S. In S, the ON-time rod position Ps is detected by the absolute angle sensor. In S, it is determined whether or not the absolute value of the difference between the OFF-time rod position Pe and the ON-time rod position Ps is larger than the determination threshold value ΔPth. When the determination in Sis YES, Sand subsequent steps are executed. When the determination in Sis NO, the OFF-time cumulative rotation number Ne is set as the count start value Ncf in S, and the counting of the rotation number of the actuatoris started.

21 26 100 27 22 25 When the determination in Sis NO, it is determined in Swhether or not the main switchis ON. When the determination is YES, Sand subsequent steps are executed without executing S-S.

27 36 5 14 50 27 31 60 56 5 FIG. In S-S, processing similar to that in S-Sof the alignment adjustment program is executed. In the rear wheel steering ECU, S-Sare executed while the rear wheel steering angle control program represented by the flowchart ofis executed. In a case where the vehicle is not inclined after the start of traveling, the straight-traveling operation amount d supplied from the EPS ECUis stored in the database.

100 34 35 56 36 When the traveling is ended and the main switchis turned to OFF, the counting of the rotation number is ended in S. In this step, the rear wheel steering control is also ended. The OFF-time cumulative rotation number Ne and the OFF-time rod position Pe are acquired in Sand are stored in the databasein S.

24 51 30 52 53 50 52 54 On the other hand, when the determination in Sis YES, Sis executed to acquire the ON-time cumulative rotation number Ns based on the ON-time rod position Ps and to set the ON-time cumulative rotation number Ns as the count start value Ncf. Then, the counting of the cumulative rotation number of the actuatoris started from the count start value Ncf in S. When the traveling is started and the determination in Sbecomes YES, the rear wheel steering ECUcontrols the rear wheel steering angle based on the cumulative rotation number Nc counted in S, and Sand subsequent steps are executed.

54 55 54 55 56 100 6 90 57 56 58 59 59 54 59 59 59 27 56 7 FIG. In Sand S, it is determined whether or not the vehicle is inclined based on the lateral acceleration. When the determinations in Sand Sare NO, the control flow proceeds to Sin which the straight-traveling operation amount d acquired when the main switchis ON this time is supplied from the EPS systemvia the CAN. In S, it is determined whether or not the absolute value |d−dm| of the difference between the straight-traveling operation amount d and the straight-traveling operation amount dm stored in the database(the previous value of the straight-traveling operation amount) is larger than the first threshold value dth. When the determination is NO, it is determined in Sand Swhether or not a state in which the absolute value |d−dm| of the difference is equal to or less than the first threshold dth has continued for a set time or more. When Sis executed for the first time, the determination result is NO. However, when S-Sare repeatedly executed and the set time elapses, the determination in Smay be YES. When the determination in Sis YES, it is determined that the correction based on the ON-time rod position Ps is appropriate, and the control flow returns to Sin. Then, the current straight-traveling operation amount d is acquired and stored in the database.

57 60 22 61 62 On the other hand, when the determination in Sis YES, the control flow proceeds to Sin which a value ΔPd acquired by converting the absolute value |d−dm| of the difference into the movement amount of the steering rodis acquired. In S, it is determined whether or not the conversion value ΔPd is equal to or smaller than the third threshold value δ. When the determination is YES, the cumulative rotation number Ne is corrected in Sbased on the straight-traveling operation amount d. In the present embodiment, the cumulative rotation number Nc is often corrected by ±1.

62 22 22 54 In S, the actual position of the steering rodis also changed in accordance with the correction of the cumulative rotation number Nc. The steering rodis moved such that the rod position corresponding to the corrected cumulative rotation number Nc matches the rod position detected by the absolute angle sensor.

10 FIG. 11 FIG. 22 22 During the control of the rear wheel steering angle, a range is assumed which is determined by the control value of the rear wheel steering angle at the time when the start of the correction is instructed and the set value. As shown in, the steering rodmay be slowly moved, triggered by a change of the control value of the rear wheel steering angle from a value within the range to a value outside the range. Further, as shown in, the steering rodmay be slowly moved, triggered by a change of the control value of the rear wheel steering angle from a value outside the range to a value within the range.

22 54 This makes it possible to move the steering rodwhile reducing an uncomfortable feeling of the driver. In addition, the relationship between the detection value of the absolute angle sensorand the cumulative rotation number Nc can be favorably maintained.

62 32 After execution of S, Sand subsequent steps are executed.

61 54 61 54 60 62 32 36 When the determination in Sis NO, on the other hand, it is determined that the reliability of the straight-traveling operation amount d is low, and the control flow returns to S. The straight-traveling operation amount d is acquired again. When the determination in Sbecomes YES by repeated execution of S-S, Sis executed, and S-Sare executed.

22 100 54 54 100 As described above, in the present embodiment, the presence or absence of the “movement” of the steering rodin the time period during which the main switchis OFF is determined based on the detection value of the absolute angle sensor. When it is determined that the “movement” has been caused, the cumulative rotation number is corrected based on the ON-time rod position detected by the absolute angle sensorwhen the main switchis turned to ON. As a result, it is possible to suppress a decrease in the control accuracy of the rear wheel steering angle in spite of the “movement”.

30 54 Further, during the control of the rear wheel steering angle, the cumulative rotation number Nc is corrected based on the straight-traveling operation amount d in a situation in which the rear wheel steering angle is not 0° and the vehicle is in the deflected traveling state. It is thus possible to correct the cumulative rotation number Nc of the actuatoreven for a part of the cumulative rotation number that cannot be corrected based on the detection value of the absolute angle sensor. As a result, the control accuracy of the rear wheel steering angle is favorably prevented from being decreased.

22 22 22 12 FIG. The position of the steering rodcan be corrected in a stopped state of the vehicle. In this case, the steering rodis forcibly moved in the stopped state of the vehicle, as shown in. It is considered that the driver feels less uncomfortable even if the steering rodis forcibly moved in the stopped state of the vehicle.

60 50 4 6 The illustrated embodiment exemplifies a case in which the straight-traveling operation amount d is supplied from the EPS ECUto the rear wheel steering ECU. The present disclosure may be embodied otherwise. For example, in a case where the rear wheel steering systemand the EPS systemare combined to constitute a vehicle steering system, both the learning of the straight-traveling operation amount d and the correction of the cumulative rotation number Nc are executed in the vehicle steering system.

92 94 92 94 50 The straight-traveling operation amount d is also acquired by the automated driving assistance ECUand the travel control ECU. Therefore, the straight-traveling operation amount d may be supplied from the automated driving assistance ECUand the travel control ECUto the rear wheel steering ECU.

102 The fact that the vehicle is in the deflected traveling state may be acquired with a camera included in the surrounding environment acquisition device. For example, it can be acquired based on a change in the captured images on the axis of the camera. The camera is provided at a front central portion of the vehicle so as to face forward.

When the vehicle is traveling straight and the traveling direction F of the vehicle coincides with the front-rear direction axis Lf, the captured images of the same object should always be located on a reference area of the camera. On the other hand, when the vehicle is in the deflected traveling state and the front-rear direction axis Lf is inclined with respect to the traveling direction F, the captured images of the same object are located at respective portions apart from the reference area of the camera. Based on this, it is possible to acquire: the fact that the vehicle is in the deflected traveling state; and the inclination of the front-rear direction axis Lf of the vehicle with respect to the traveling direction F of the vehicle.

Further, the fact that the vehicle is in the deflected traveling state may be acquired based on each of positions detected by respective two position detection devices (such as GPS receivers) provided apart from each other in the width direction of the vehicle or each of movement trajectories or the like that is based on a change in each of the positions.

30 The actuatormay include a speed reducer. Further, the in-vehicle device is not limited to the rear wheel steering system or the constituent elements thereof. Further, the set state is not limited to the straight traveling state but may be a turning traveling state, for example.

50 52 54 58 60 72 86 As described above, in the present embodiment, the rear wheel steering ECU, the resolver, the absolute angle sensor, the lateral acceleration sensor, the EPS ECU, the operation state detecting device, the yaw rate sensor, and the like constitute an operation amount acquisition device.

70 24 4 30 52 70 72 22 54 56 The straight-traveling operation amount d of the steering operation memberis one example of an inclination-related value that is the inclination of the front-rear direction axis Lf with respect to the traveling direction F of the vehicle. The moving force applying deviceor the rear wheel steering systemcorresponds to the in-vehicle device. The cumulative rotation number of the actuatorcorresponds to the operation amount, and the resolverand the like constitute an operation amount detecting device. Further, the straight-traveling operation amount d of the steering operation membercorresponds to a first physical quantity, and the operation state detecting devicecorresponds to a first physical quantity detecting device and an inclination-related value detecting portion. The position of the steering rodcorresponds to a second physical quantity, and the absolute angle sensorcorresponds to a second physical quantity detecting device and a rod position detecting portion. The OFF-time rod position Pe corresponds to an OFF-time second physical quantity, and the ON-time rod position Ps corresponds to an ON-time second physical quantity and a detected rod position. The detected inclination-related value corresponds to a current value d of the straight-traveling operation amount, and the reference inclination-related value corresponds to the straight-traveling operation amount dm stored in the database.

50 21 62 21 62 24 24 The rear wheel steering ECUand the like constitute a control device. A portion of the control device that stores S-S, a portion of the control device that executes S-S, and the like constitute an operation amount correcting portion. A portion of the control device that stores S, a portion of the control device that executes S, and the like constitute a movement determining portion.

In addition, the present disclosure may be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

(1) An operation amount acquisition device configured to acquire an operation amount of an actuator in a rear wheel steering system, the rear wheel steering system including a steering rod extending in a width direction of a vehicle and the actuator capable of moving the steering rod in the width direction, the rear wheel steering system being configured to steer at least one of a left rear wheel and a right rear wheel of the vehicle connected to the steering rod by causing the actuator to move the steering rod in the width direction, wherein the rear wheel steering system includes a control device configured to control a steering angle of the at least one of the left rear wheel and the right rear wheel based on the operation amount of the actuator, and wherein the operation amount acquisition device includes: an operation amount detecting device configured to detect the operation amount of the actuator; an inclination-related value detecting portion configured to detect an inclination-related value that is related to an inclination of a front-rear direction axis of the vehicle with respect to a traveling direction of the vehicle; and an operation amount correcting portion configured to correct, based on a detected inclination-related value that is the inclination-related value detected by the inclination-related value detecting portion, the operation amount of the actuator detected by the operation amount detecting device in a state in which the steering angle of the at least one of the left rear wheel and the right rear wheel is controlled by the control device based on the operation amount of the actuator detected by the operation amount detecting device such that the vehicle is in a straight traveling state. There will be described various forms of the claimable invention.

(2) The operation amount acquisition device according to the form (1), wherein the operation amount correcting portion corrects the operation amount of the actuator based on the detected inclination-related value when an absolute value of a difference between the detected inclination-related value and a reference inclination-related value is larger than a first threshold value, the reference inclination-related value being the inclination-related value in the straight traveling state of the vehicle acquired and stored in advance. The inclination-related value is the inclination of the front-rear direction axis of the vehicle with respect to the traveling direction of the vehicle or a value corresponding to the inclination on a one-to-one basis. When the rear wheel steering angle is controlled such that the vehicle is in the straight traveling state, the target rear wheel steering angle is often made equal to 0°.

(3) The operation amount acquisition device according to the form (1) or (2), wherein the rear wheel steering system includes a rod position detecting portion configured to detect a position of the steering rod that is a displacement of the steering rod from a neutral position of the steering rod, and wherein the operation amount correcting portion corrects the operation amount of the actuator based on an ON-time rod position when an absolute value of a difference between an OFF-time rod position and the ON-time rod position is larger than a second threshold value, the OFF-time rod position being the position of the steering rod acquired based on the operation amount of the actuator detected by the operation amount detecting device when a main switch of the vehicle is switched from ON to OFF, the ON-time rod position being the position of the steering rod detected by the rod position detecting portion when the main switch is switched from OFF to ON. The reference inclination-related value may be, for example, an inclination-related value acquired when the main switch was ON in the past. The reference inclination-related value is a value when the vehicle is not in the deflected traveling state. Therefore, the first threshold value may be a value by which the vehicle can be considered to be in the deflected traveling state.

(4) The operation amount acquisition device according to the form (3), wherein the operation amount correcting portion corrects, based on the detected inclination-related value, a corrected operation amount that is the operation amount of the actuator corrected based on the ON-time rod position when (A) an absolute value of a difference between the detected inclination-related value and a reference inclination-related value is larger than a first threshold value and (B) a value acquired by converting the absolute value of the difference between the detected inclination-related value and the reference inclination-related value into a movement amount of the steering rod is smaller than a third threshold value, the detected inclination-related value being detected by the inclination-related value detecting portion in a state in which the steering angle of the at least one of the left rear wheel and the right rear wheel is controlled by the control device based on the corrected operation amount such that the vehicle is in the straight traveling state, the reference inclination-related value being the inclination-related value in the straight traveling state of the vehicle acquired and stored in advance. The second threshold value may be a value by which it can be determined that the steering rod has been moved. Further, the second threshold value is desirably a value equal to or larger than a tolerance of the rod position detecting portion.

107 108 (5) The operation amount acquisition device according to any one of the forms (1)-(4), wherein the rear wheel steering system includes a rod position detecting portion configured to detect a position of the steering rod that is a displacement of the steering rod from a neutral position of the steering rod, and wherein the operation amount acquisition device includes a movement determining portion that determines that the steering rod has been moved by an external force in a time period during which a main switch of the vehicle is OFF when an absolute value of a difference between an OFF-time rod position and an ON-time rod position is larger than a second threshold value, the OFF-time rod position being the position of the steering rod acquired based on the operation amount of the actuator detected by the operation amount detecting device when the main switch is switched from ON to OFF, the ON-time rod position being the position of the steering rod detected by the rod position detecting portion when the main switch is switched from OFF to ON. (6) The operation amount acquisition device according to any one of the forms (1)-(5), wherein the actuator includes a motor, and wherein the operation amount detecting device detects the number of rotations of the actuator to acquire the cumulative number of rotations of the actuator from a neutral position of the actuator. (7) The operation amount acquisition device according to any one of the forms (1)-(6), wherein the inclination-related value detecting portion detects, as the inclination-related value, at least one of (a) an operation amount of a steering operation member provided in the vehicle from a neutral position of the steering operation member; and (b) an inclination of an axis of a camera with respect to the traveling direction of the vehicle, the camera being mounted on the vehicle so as to be capable of capturing images ahead of the vehicle. (8) The operation amount acquisition device according to any one of the forms (1)-(7), wherein the rear wheel steering system includes a rod position detecting portion configured to detect a position of the steering rod that is a displacement of the steering rod from a neutral position of the steering rod, and wherein a change amount of the inclination-related value that changes in accordance with a change in a set operation change amount of the operation amount of the actuator is larger than a tolerance of the inclination-related value detecting portion, and a movement amount of the steering rod that changes in accordance with the change in the set operation change amount of the operation amount is smaller than a tolerance of the rod position detecting portion. The third threshold value may be a value determined based on the tolerance of the rod position detecting portion. The corrected operation amount corresponds to the cumulative rotation number that starts to be counted by execution of Sand Sin the illustrated embodiment.

(9) A steering system, including: a steering rod extending in a width direction of a vehicle and connected to a wheel; an actuator capable of moving the steering rod in the width direction; an operation amount detecting device configured to detect an operation amount of the actuator; a rod position detecting portion configured to detect a position of the steering rod that is a displacement of the steering rod from a neutral position of the steering rod; and an operation amount correcting portion that corrects the operation amount based on an ON-time rod position when an absolute value of a difference between an OFF-time rod position and the ON-time rod position is larger than a second threshold value, the OFF-time rod position being the position of the steering rod acquired based on the operation amount when a main switch of the vehicle is switched from ON to OFF, the ON-time rod position being the position of the steering rod detected by the rod position detecting portion when the main switch is switched from OFF to ON. The above form is a basic requirement representing the performance of each detecting portion. The set operation change amount may be, for example, the set rotation number of the actuator. In the illustrated embodiment, the set rotation number is 1.

(10) A steering system, including: a steering rod extending in a width direction of a vehicle and connected to a wheel; an actuator capable of moving the steering rod in the width direction; an operation amount detecting device configured to detect an operation amount of the actuator; a rod position detecting portion configured to detect a position of the steering rod that is a displacement of the steering rod from a neutral position of the steering rod; and a movement determining portion that determines that the steering rod has been moved in the width direction by an external force in a time period during which a main switch of the vehicle is OFF when an absolute value of a difference between an OFF-time rod position and an ON-time rod position is larger than a second threshold value, the OFF-time rod position being the position of the steering rod acquired based on the operation amount when the main switch is switched from ON to OFF, the ON-time rod position being the position of the steering rod detected by the rod position detecting portion when the main switch is switched from OFF to ON. The steering system according to this form may employ the features described in any one of the forms (1)-(8).

(11) An operation amount acquisition device, including: an operation amount detecting device configured to detect an operation amount of an actuator of an in-vehicle device mounted on a vehicle; a first physical quantity detecting device configured to detect a first physical quantity that is a physical quantity corresponding to the operation amount on a one-to-one basis; and an operation amount correcting portion configured to correct the operation amount based on the first physical quantity detected by the first physical quantity detecting device, wherein the operation amount correcting portion corrects the operation amount of the actuator based on a value detected by the first physical quantity detecting device when the vehicle is traveling in a predetermined set state while the actuator is controlled based on the operation amount detected by the operation amount detecting device. The steering system according to this form may employ the features described in any one of the forms (1)-(9).

One example of the first physical quantity detecting device is the inclination-related value detecting portion, and one example of the set state of the vehicle is the straight traveling state of the vehicle. One example of the in-vehicle device is the rear wheel steering system or the constituent elements of the rear wheel steering system. The first physical quantity detecting device and the in-vehicle device are not limited to those in the illustrated embodiment.

(12) The operation amount acquisition device according to the form (11), further including a second physical quantity detecting device that is different from the first physical quantity detecting device and that is configured to detect a second physical quantity different from the first physical quantity and corresponding to the operation amount on a one-to-one basis, wherein the operation amount correcting portion does not correct the operation amount based on a second detection value when an absolute value of a difference between a second conversion value and the second detection value is smaller than a fourth threshold value, and the operation amount correcting portion corrects the operation amount based on the second detection value when the absolute value of the difference is equal to or larger than the fourth threshold value, the second conversion value being a value acquired by converting the operation amount detected by the operation amount detecting device into the second physical quantity, the second detection value being a value detected by the second physical quantity detecting device. The operation amount acquisition device of this form may employ the technical features described in any one of the forms (1)-(10).

(13) The operation amount acquisition device according to the form (11) or (12), wherein the operation amount correcting portion determines that a first detection value is abnormal when a differential second conversion value is equal to or larger than a fifth threshold value, and the operation amount correcting portion corrects, based on the first detection value, a corrected operation amount corrected based on the second detection value when the differential second conversion value is smaller than the fifth threshold value, the differential second conversion value being a value acquired by converting, into the second physical quantity, an absolute value of a difference between the first detection value and a first reference value, the first detection value being a value detected by the first physical quantity detecting device when the vehicle is traveling in the set state while the in-vehicle device is controlled based on the corrected operation amount, the first reference value being the first physical quantity in traveling of the vehicle in the set state acquired and stored in advance. In the illustrated embodiment, the second detection value corresponds to the ON-time rod position Ps, and the second conversion value corresponds to the OFF-time rod position Pe. The fourth threshold value corresponds to the second threshold value.

The fifth threshold value corresponds to the third threshold value.